1. Field of the Invention
The invention relates to a self-contained round for a large caliber artillery or anti-tank weapon and in particular a round including electrically-detonated secondary explosives for accelerating a projectile to hypervelocity speeds.
2. Description of Related Art
Current large caliber projectiles travel at relatively low speeds. In most cases, the speeds are slightly subsonic (approximately 900 ft./sec.). These speeds may be augmented for high penetration devices (approximately 3,000 ft./sec.). These relatively low speed projectiles require flight time for one kilometer (neglecting drag) of approximately 3.6 seconds. This long flight time requires consideration of the effects of target motion, wind, gravity, and other trajectory perturbations. For example, a target moving 15 meters per second moves 54 feet during a 3.6 second flight time. This lead must be included in the aim of a weapon.
One method developed for terminal kills that uses a high speed projectile is based on the self-forging fragmentation warhead. In this design, the warhead is triggered and melts the liner. Molten droplets of the liner are accelerated to speeds of between 8,000 to 12,000 ft./sec. The metal fragments strike the target causing damage. Such warheads, however, are range limited to approximately 200 ft., due in part to the irregular shape of the warhead fragments which are not aerodynamically efficient. High drag acting on the irregular fragments cause them to lose speed rapidly.
The concept of using secondary explosives in weapons to accelerate projectiles has long been known. U.S. Pat. No. 241,978, which issued in 1881, is directed to a gun incorporating secondary explosives disposed to act on the projectile during its travel through the barrel of the gun. The patented device required a complex construction of a gun barrel to permit location of powder charges which are selectively detonated, the gas from which adds acceleration to the projectile. Other similar concepts are shown in U.S. Pat. Nos. 484,009, 2,360,217, and 3,459,101.
Other apparatus for accelerating projectiles are taught in U.S. Pat. Nos. 3,411,403 and 3,418,878. In these patents, a moving projectile is introduced into a disposable explosive lined barrel. The friction from the projectile passing through the barrel ignites the explosive generating gas to further accelerate the projectile. The patents do not suggest how the concept would be used in a weapon in view of the disposable nature of the barrel and the need for another device to accelerate the projectile prior to entry into the barrel.
Finally, U.S. Pat. No. 3,031,933 teaches an explosive linear accelerator including a plurality of axially-adjacent, coaxial, annular explosive charges supported on a rack structure and defining a bore for passage of a projectile. The device includes a complex electrical system for detonating in succession the annular explosive charges in response to passage of the projectile through the bore. No consideration is given for use of the device as a weapon.
The subject invention is directed to a self-contained round for use large caliber artillery or anti-tank weapon. The round includes a projectile a primary charge, secondary charges, and means for selectively activating the secondary charges in order to accelerate the projectile within the cartridge case of the round. The round of the invention, in one embodiment, may be used in existing large caliber weapons. This is distinct from the prior efforts discussed above in which the secondary acceleration mechanism is incorporated into the gun rather than the cartridge or in which the entire concept is of the laboratory type not amenable to use in a self-contained cartridge.
Additional advantages of the invention are set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.